diff --git a/library/core/src/main/java/com/google/android/exoplayer2/source/ExtractorMediaPeriod.java b/library/core/src/main/java/com/google/android/exoplayer2/source/ExtractorMediaPeriod.java
index d4ea6191aa..63c86c2c96 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/source/ExtractorMediaPeriod.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/source/ExtractorMediaPeriod.java
@@ -90,7 +90,7 @@ import java.util.Arrays;
   private final Runnable onContinueLoadingRequestedRunnable;
   private final Handler handler;
 
-  private Callback callback;
+  private @Nullable Callback callback;
   private SeekMap seekMap;
   private SampleQueue[] sampleQueues;
   private int[] sampleQueueTrackIds;
@@ -190,6 +190,7 @@ import java.util.Arrays;
     }
     loader.release(this);
     handler.removeCallbacksAndMessages(null);
+    callback = null;
     released = true;
     eventDispatcher.mediaPeriodReleased();
   }
diff --git a/library/dash/src/main/java/com/google/android/exoplayer2/source/dash/DashMediaPeriod.java b/library/dash/src/main/java/com/google/android/exoplayer2/source/dash/DashMediaPeriod.java
index d2982481e0..f80ff89fc1 100644
--- a/library/dash/src/main/java/com/google/android/exoplayer2/source/dash/DashMediaPeriod.java
+++ b/library/dash/src/main/java/com/google/android/exoplayer2/source/dash/DashMediaPeriod.java
@@ -16,6 +16,7 @@
 package com.google.android.exoplayer2.source.dash;
 
 import android.support.annotation.IntDef;
+import android.support.annotation.Nullable;
 import android.util.Pair;
 import android.util.SparseArray;
 import android.util.SparseIntArray;
@@ -72,7 +73,7 @@ import java.util.List;
   private final IdentityHashMap<ChunkSampleStream<DashChunkSource>, PlayerTrackEmsgHandler>
       trackEmsgHandlerBySampleStream;
 
-  private Callback callback;
+  private @Nullable Callback callback;
   private ChunkSampleStream<DashChunkSource>[] sampleStreams;
   private EventSampleStream[] eventSampleStreams;
   private SequenceableLoader compositeSequenceableLoader;
@@ -150,6 +151,7 @@ import java.util.List;
     for (ChunkSampleStream<DashChunkSource> sampleStream : sampleStreams) {
       sampleStream.release(this);
     }
+    callback = null;
     eventDispatcher.mediaPeriodReleased();
   }
 
diff --git a/library/hls/src/main/java/com/google/android/exoplayer2/source/hls/HlsMediaPeriod.java b/library/hls/src/main/java/com/google/android/exoplayer2/source/hls/HlsMediaPeriod.java
index 1a3f41fffc..b142d38df9 100644
--- a/library/hls/src/main/java/com/google/android/exoplayer2/source/hls/HlsMediaPeriod.java
+++ b/library/hls/src/main/java/com/google/android/exoplayer2/source/hls/HlsMediaPeriod.java
@@ -15,6 +15,7 @@
  */
 package com.google.android.exoplayer2.source.hls;
 
+import android.support.annotation.Nullable;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.Format;
 import com.google.android.exoplayer2.SeekParameters;
@@ -57,7 +58,7 @@ public final class HlsMediaPeriod implements MediaPeriod, HlsSampleStreamWrapper
   private final CompositeSequenceableLoaderFactory compositeSequenceableLoaderFactory;
   private final boolean allowChunklessPreparation;
 
-  private Callback callback;
+  private @Nullable Callback callback;
   private int pendingPrepareCount;
   private TrackGroupArray trackGroups;
   private HlsSampleStreamWrapper[] sampleStreamWrappers;
@@ -96,6 +97,7 @@ public final class HlsMediaPeriod implements MediaPeriod, HlsSampleStreamWrapper
     for (HlsSampleStreamWrapper sampleStreamWrapper : sampleStreamWrappers) {
       sampleStreamWrapper.release();
     }
+    callback = null;
     eventDispatcher.mediaPeriodReleased();
   }
 
diff --git a/library/smoothstreaming/src/main/java/com/google/android/exoplayer2/source/smoothstreaming/SsMediaPeriod.java b/library/smoothstreaming/src/main/java/com/google/android/exoplayer2/source/smoothstreaming/SsMediaPeriod.java
index 9a0d57ff31..8e7c3e38c9 100644
--- a/library/smoothstreaming/src/main/java/com/google/android/exoplayer2/source/smoothstreaming/SsMediaPeriod.java
+++ b/library/smoothstreaming/src/main/java/com/google/android/exoplayer2/source/smoothstreaming/SsMediaPeriod.java
@@ -15,6 +15,7 @@
  */
 package com.google.android.exoplayer2.source.smoothstreaming;
 
+import android.support.annotation.Nullable;
 import android.util.Base64;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.SeekParameters;
@@ -52,7 +53,7 @@ import java.util.ArrayList;
   private final TrackEncryptionBox[] trackEncryptionBoxes;
   private final CompositeSequenceableLoaderFactory compositeSequenceableLoaderFactory;
 
-  private Callback callback;
+  private @Nullable Callback callback;
   private SsManifest manifest;
   private ChunkSampleStream<SsChunkSource>[] sampleStreams;
   private SequenceableLoader compositeSequenceableLoader;
@@ -98,6 +99,7 @@ import java.util.ArrayList;
     for (ChunkSampleStream<SsChunkSource> sampleStream : sampleStreams) {
       sampleStream.release();
     }
+    callback = null;
     eventDispatcher.mediaPeriodReleased();
   }